PCNC research and development laboratory


New Approaches to Building NC Systems for Intelligent Control

Vladimir L. Sosonkin, Georgi M. Martinov

The course of events in AI (Artificial Intelligence) is rather well known. There are attempts to use AI-elements in numerical control systems. Nevertheless, these attempts do not define the direction of efforts now, at the time when numerical control systems of a new generation are being developed. The main goal is to make control system an inexpensive, convenient, effective and reliable tool in the industrial environment. Thus, the conception of modern intelligent control systems has its unique features, connected with the latest computer technology. Among the unique features of the Intelligent Control Systems are their configurability and open architecture, the ability of their man-machine interface (MMI) to satisfy users requirements, the effectiveness and convenience of their operators work. Besides, they deliver exhaustive information about themselves and their objectives. All Intelligent Control Systems belong to PCNC type. Two approaches exist to select their architecture, the two-computer and the one-computer version. Both include PC-and NC-subsystems, and both have three-layer structures. The bottom layer consists of the computer- and the PLC-hardware, that represent the input-output controllers. The second level includes the operation and communication systems, while the top layer, the application. Either version of the Intelligent Control Systems requires object-oriented approach. The basic application components are represented by "control tasks", which include terminal, geometric, logical, technological, and dispatcher tasks. Each task is a module with some standard API-interface. The object-oriented channel is the only global communication facility for control tasks and modules. Its components fulfill services, such as delivery of the information by means of transactions, control processes, dialogue and configuration. They also execute miscellaneous functions and work with different data types. Configurability allows to adjust the system to any ISO-7bit (DIN 66025) language, to use customer versions of operators dialogue and screen structure, and to include any commercial program modules into the MMI shell. MMI plays an important role in intelligent PCNCs, serving as a means of revealing their functionality. A PCNC user would like to have an MMI, most convenient for his individual dialogue regiment and information contents of the screen. Therefore, MMI should be flexible and configurable; it needs to allow dialogue corrections or redefinition. MMI development includes complicated tasks, such as dialogue implementation and interpretation.

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